Processes for treatment of residuals

ABSTRACT

There are provided processes for treating a residual. For example, such processes can comprise treating a mixture comprising the residual, a peracid or source thereof and an ammonium salt in a reactor, with an electric field, by means of at least one anode and at least one cathode that define therebetween an electrokinetic zone for treating the mixture. Such processes allow for inactivation of at least one type of pathogen in the residual so as to obtain a treated residual.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of Ser. No. 14/438,123 filedon Apr. 23, 2015 that is a 35 USC 371 national stage entry ofPCT/CA2013/000924 filed on Oct. 25, 2013 and which claims priority toU.S. 61/718,386 filed on Oct. 25, 2012. These documents are herebyincorporated by reference their entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to improvements in the field ofresiduals (for example, biosolids, sludge and sediments) treatment. Forexample, it relates to processes for the treatment of a residual thatallow for inactivation of at least one type of pathogen in the residualso as to obtain a treated residual. For example, the treated residualcan be suitable for an agricultural purpose.

BACKGROUND OF THE DISCLOSURE

Wastewater treatment plants in Canada produce about 860,000 dry tons peryear of sewage residuals (TS); Montréal, Québec generates approx. 270 tTS/day. In Europe, the UK generates 1,640,000 t dry TS/year where 70% isused for land application while in Germany, 20% of its almost 2 billiontons per year of dry solids was applied to land in 2010 (Oleszkiewicz,2012). Landfilling, incineration and land application are three mainoptions for residuals disposal. As landfilling and incineration eachhave their own environmental disadvantages, regulators favoragricultural land application of residuals. For example, Section 5.6.8of the Québec Residual Materials Management Policy 1998-2008 (Québec,2000) states: “The ultimate goal is to ensure that no sludge islandfilled until it has been demonstrated that recovery is not aneconomically viable option.”

It is estimated that land application of residuals contributes more than$55M a year to the economy. However, residuals, for example, may containpathogens from a fecal source which may threaten human health if theresiduals are not used safely in accordance with good practice.Therefore, complex regulatory systems, e.g., the Bureau de normalisationdu Québec (BNQ) standards, have been developed for reusing residualswith the intention of protecting human, animal and plant health, groundand surface water quality, enduring soil quality and soil biodiversity.These regulations encourage municipal wastewater treatment facilities totreat residuals to a higher quality level and minimize constraints onuse; and require relatively expensive management practices, furtherassuring clean and safe beneficial uses for residuals.

Such treatment should be designed to improve the characteristics of theresiduals for a disposal practice, increase the economic feasibility ofusing a particular practice and reduce the potential for public health,environmental and nuisance problems. Conventional technologies such astime-temperature regimes, high pH-high temperature processes, alkalinetreatment by adding lime, beta ray irradiation, gamma ray irradiationand use of a mesophilic anaerobic digester are usually not effectiveenough, and are usually time-consuming and expensive. Further, otherissues and trends including the push for lower greenhouse gasproduction, reducing dioxins/furans and polychlorinated biphenyls(PCBs), decreasing time and energy requirements, availability of landand acceptability of present practices will affect the selection of aprocess for residuals treatment.

Electrokinetic treatment is based on the application of, for example,direct current (DC) within a contaminated matrix to remove, for example,pollutants through several electrokinetic phenomena. While it has beenused in soil remediation for many years, electrokinetic treatment ofresiduals is a novel application of such technology in environmentalpractice.

SUMMARY OF THE DISCLOSURE

According to one aspect, there is provided a process for treating aresidual, said process comprising:

treating a mixture comprising the residual, a peracid or source thereofand an ammonium salt in a reactor, with an electric field, by means ofat least one anode and at least one cathode that define therebetween anelectrokinetic zone for treating the mixture,

thereby allowing for inactivation of at least one type of pathogen inthe residual so as to obtain a treated residual.

According to another aspect, there is provided a process for treating aresidual, said process comprising:

treating a mixture comprising the residual, a peracid or source thereofand an ammonium salt in a reactor, with an electric field, by means ofat least one anode and at least one cathode that define therebetween anelectrokinetic zone for treating the mixture,

thereby allowing for destruction of at least one type of pathogen in theresidual so as to obtain a treated residual.

According to another aspect, there is provided a process for treating aresidual, said process comprising:

treating a mixture comprising the residual, a peracid or a sourcethereof and an ammonium salt, in a reactor, with an electric field, bymeans of at least one anode and at least one cathode that definetherebetween an electrokinetic zone for treating the mixture,

thereby allowing for simultaneous inactivation and/or destruction of atleast one type of pathogen in the residual and dewatering of theresidual, so as to obtain a treated dewatered residual and separatedwater.

It has been shown in the present disclosure that treating a mixturecomprising a residual, a peracid or a source thereof and an ammoniumsalt, for example, ammonium nitrate with, for example, a low voltagegradient in a direct current electric field can simultaneously dewaterand inactivate and/or destroy at least one type of pathogen from theresidual, producing treated a dewatered residual and separated water.The processes of the present disclosure can, for example, raise thetemperature of the mixture, change the chemical properties of theresidual, change the physiological properties of Clostridium perfringensspores present in the residual, for example, cause the spores togerminate, destroying most pathogens and creating an environment thatwill not support future pathogen regrowth. The processes of the presentdisclosure, for example, enhance the ionic strength, cause an exothermicreaction and increase the biocidal stressors/constituents present in thesystem. The processes of the present disclosure can, for example,provide disinfection, or pasteurization, or sterilization of theresidual.

Unlike some prior art processes, the treated residual can, for example,be suitable for agricultural purposes because, for example, the ammoniumsalt may not create byproducts which can be harmful to human health insuch a way that human exposure to them needs to be restricted. Theprocesses of the present disclosure have been shown, for example, to beeffective in destroying one of the most resistant forms of amicroorganism, Clostridium perfringens spores, from anaerobicallydigested residuals within a fast time of less than two hours. It shouldbe noted that under anaerobic conditions, C. perfringens spores are, forexample, the most resistant microbe and a three log reduction indicatesClass A disinfection with respect to viruses, bacteria and helminth eggs(Blanker et al., 1992). Compared to other methods for producingresiduals of a high standard (for example, P1 or Class A biosolids) theprocesses of the present disclosure are expected to be inexpensive bothin initial capital expenditure and ongoing operation and maintenancecosts.

Other features and advantages of the present disclosure will becomeapparent from the following detailed description. It should beunderstood, however, that the detailed description and the specificexamples while indicating embodiments of the present disclosure aregiven by way of illustration only, since various changes andmodifications within the scope of the present disclosure will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings represent examples that are presented in anon-limitative manner:

FIG. 1 is a schematic representation of a reactor for treating residualsin accordance with an example of the present disclosure;

FIG. 2A is a front view of an electrode for use in a reactor fortreating residuals in accordance with an example of the presentdisclosure, while FIG. 2B is a top view of the same electrode;

FIG. 3 is an exemplary transmission electron microscope (TEM) micrographshowing the creation of nicks in Clostridium perfringens spore membranes(black arrow) after treatment by a process of the present disclosure;

FIG. 4 is a schematic representation of the treatment reactionsaccording to a process of the present disclosure;

FIG. 5 is a schematic representation of the lethal pathways in a C.perfringens spore according to a process of the present disclosure; and

FIG. 6 is an exemplary plot showing the log reduction of Clostridiumperfringens spores over time in anaerobically digested residuals treatedwith a process of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Unless otherwise indicated, the definitions and embodiments described inthis and other sections are intended to be applicable to all embodimentsand aspects of the application herein described for which they aresuitable as would be understood by a person skilled in the art.

As used in this application, the singular forms “a”, “an” and “the”include plural references unless the content clearly dictates otherwise.For example, an embodiment including “a residual” should be understoodto present certain aspects with one type of residual, or two or moreadditional types of residuals. For example, an embodiment including a“pathogen” should be understood to present certain aspects with one typeof pathogen, or two or more additional types of pathogens. For example,an embodiment including “a biosolid” should be understood to presentcertain aspects with one type of biosolid, or two or more additionaltypes of biosolids.

In embodiments comprising an “additional” or “second” component, such asan additional or second type of residual, or an additional or secondtype of pathogen, the second component as used herein is different fromthe other components or first component. A “third” component isdifferent from the other, first, and second components, and furtherenumerated or “additional” components are similarly different.

In understanding the scope of the present disclosure, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. The term “consisting” and its derivatives, as used herein,are intended to be closed terms that specify the presence of the statedfeatures, elements, components, groups, integers, and/or steps, butexclude the presence of other unstated features, elements, components,groups, integers and/or steps. The term “consisting essentially of”, asused herein, is intended to specify the presence of the stated features,elements, components, groups, integers, and/or steps as well as thosethat do not materially affect the basic and novel characteristic(s) offeatures, elements, components, groups, integers, and/or steps.

The term “residual” as used herein refers, for example, to a solidmatter comprising at least one type of organic matter or at least onetype of colloid. For example, the residual can be a sludge comprising atleast one organic compound or at least one organic matter. For example,the residual can be a biosolid, sewage sludge, an industrial sludge,pulp and paper or mining residuals, a sediment, a deposition, anagricultural sludge, a waste solid or a slurry. For example, theresidual can be a medical science residual, a food residual, anagricultural residual, an industrial residual, a mining residual, amining sludge or slurry. For example, the residual can be human sewage.For example, the residual can be a sediment.

Terms of degree such as “about” and “approximately” as used herein meana reasonable amount of deviation of the modified term such that the endresult is not significantly changed. These terms of degree should beconstrued as including a deviation of at least ±5% or at least ±10% ofthe modified term if this deviation would not negate the meaning of theword it modifies.

The expression “low voltage gradient” as used herein refers to, forexample, an electric field having an intensity gradient of less thanabout 8 V/cm. The current can be DC or AC current.

The term “AN” as used herein refers to ammonium salts.

The term “BS” as used herein refers to Bioxy S.

The term “LIDEF” as used herein refers to low intensity direct electricfield.

The term “DPA” as used herein refers to dipicolinic acid.

The expression “source of peracid” in respect to the expression “peracidor source thereof” and the like as used herein refers, for example, to acomposition effective for generating a peracid in situ. The source ofperacid can be a solid composition, for example, a composition in powderform. For example, the source of peracid can be a composition comprisinga peroxygen source and an acylating agent. The composition can furthercomprise at least one of an acid, a sequestering agent, a surfactant anda corrosion inhibitor. The choice of a source of peracid is within thecapability of one skilled in the art. For example, the composition BioxyS™ disclosed in Canadian Patent Application No. 2,569,025 can be used asa source of peracid.

The term “peroxygen source” as used herein refers, for example, to acompound or composition effective for generating active oxygen species,for example, hydrogen peroxide, in situ. For example, the peroxygensource can be chosen from a percarbonate, a perborate and a persulfate.For example, the peroxygen source can be a percarbonate. For example,the percarbonate can be sodium carbonate peroxyhydrate. The choice of aperoxygen source is within the capability of one skilled in the art.

The term “acylating agent” as used herein refers, for example, to acompound which acts as a source of the corresponding peracylate anionand/or a source of the corresponding peracid upon reaction in situ withthe peroxygen source. For example, the acylating agent can be anacetylating agent. For example, the acetylating agent can be tetraacetylethylene diamine (TAED), which can act as a source of peracetate anionand/or peracetic acid upon reaction in situ with a peroxygen source, forexample, sodium carbonate peroxyhydrate. The choice of an acylatingagent is within the capability of one skilled in the art.

The expression “inactivation of at least one type of pathogen in theresidual” as used herein refers, for example, to an inactivation and/ordestruction of the pathogen in the residual, for example, ananaerobically digested sewage sludge to at least about a Class Adisinfection level. For example, in the case of Clostridium perfringensspores, the expression “inactivation of at least one type of pathogen inthe residual” as used herein refers, for example, to an inactivationand/or destruction, in the residual of at least about a 3 log reductionof Clostridium perfringens spores. It should be noted that underanaerobic digestion, the C. perfringens spore is a considerablyresistant microbe, and a three log reduction indicates Class Adisinfection with respect to viruses, bacteria and helminth eggs(Blanker et al., 1992). An about a three log reduction means about a99.9% reduction.

The term “disinfection” or “disinfecting” and the expression “todisinfect” as used herein refers, for example, to the inactivation of atleast 3 log of the at least one type of pathogen.

The term “pasteurization” as used herein refers, for example, toinactivation by about 4 to about 5 log of the at least one type ofpathogen exposed, for example, for a period of at least 30 min to theprocesses of the present disclosure.

The expression “high level of disinfection” or the expression “todisinfect” as used herein refers, for example, to destroy pathogens byat least 5 log, for example where a majority of the members of the atleast one type of pathogen are killed.

The term “sterilization” or the expression “to sterilize” as used hereinmeans, for example, to inactivate or destroy the at least one type ofpathogen at more than about 8 log, where, for example, almost all of themembers of the at least one type of pathogen are killed.

The expression “near sterilizing” or “near sterilization” as used hereinmeans, for example, to inactivate or destroy the at least one type ofpathogen at about 7 to about 8 log, where, for example, almost all ofthe members of the at least one type of pathogen are killed.

The term “inactivating” or “inactivation” or the expression “toinactivate” as used herein refers, for example, to render the at leastone type of pathogen unable to grow/replicate.

The term “destroy” or “destruction” as used herein refers, for example,to kill the at least one type of pathogen.

The expression “electrokinetic zone” as used herein refers to, forexample, a zone disposed between electrodes, wherein electrokineticphenomena have been generated by applying an electrical current betweena plurality of electrodes, for example, four electrodes, so that atleast one electrode functions as an anode and at least one electrodefunctions as a cathode.

The expression “adequate inactivation conditions in the reactor aremaintained” as used herein refers to, for example, maintaining theconditions in the reactor so that they will allow for inactivationand/or destruction of at least one type of pathogen in the residual. Forexample, parameters such as the time, pH, temperature, initialconcentration of solids, and initial concentration of pathogens may bevaried. The choice of conditions so that they will allow forinactivation and/or destruction of at least one type of pathogen in theresidual (for example, so that pasteurization is reached) orinactivation and/or destruction of a majority of viable pathogens, ovaand spores (for example, so that sterilization is reached) is within thecapability of a person skilled in the art, particularly with referenceto the present disclosure.

For example, the voltage gradient of the electric field can be a lowvoltage gradient.

For example, the electric field can be a direct current electric fieldor an alternating current electric field.

For example, the voltage gradient of the direct current electric fieldcan be less than about 8 V/cm.

For example, the processes of the present disclosure can furthercomprise simultaneous dewatering of the residual so as to obtain atreated dewatered residual and separated water.

For example, the mixture comprising the residual, the peracid or sourcethereof and the ammonium salt can be prepared by adding the peracid orsource thereof and ammonium salt to the residual. For example, themixture comprising the residual, the peracid or source thereof and theammonium salt can be prepared outside of the reactor, then dispersedinto the reactor prior to commencing treating the mixture.

For example, the ratio of the peracid or source thereof to the ammoniumsalt can be less than about 5 g/g. For example, the ratio of the peracidor source thereof to the ammonium salt can be about 0.1 g/g to about 5g/g. For example, the ratio of the peracid or source thereof to theammonium salt can be about 0.5 g/g to about 5 g/g. For example, theratio of the peracid or source thereof to the ammonium salt can be about1 g/g to about 5 g/g. For example, the ratio of the peracid or sourcethereof to the ammonium salt can be about 2 g/g to about 5 g/g.

For example, the ratio of the peracid or source thereof and the ammoniumsalt to the residual can be less than about 40 g/L. For example, theratio of the peracid or source thereof and the ammonium salt to theresidual can be from about 7 g/L to about 26 g/L.

For example, in the processes of the present disclosure, adequateinactivation conditions in the reactor can be maintained.

For example, the mixture can be treated for a time of less than about 4hours. For example, the mixture can be treated for a time of about 0.5hours to about 3 hours. For example, the mixture can be treated for atime of less than about 0.5 hours. For example, the mixture can betreated for a time of less than about 3 hours.

For example, the mixture can be treated at a temperature of below about70° C. For example, the mixture can be treated at a temperature of about70° C. to about 95° C. For example, the mixture can be treated at atemperature of above about 95° C. For example, the mixture can betreated until it reaches a temperature of about 99° C. For example, themixture can be treated until it reaches a temperature of about 97° C.

For example, the mixture can be treated at a pH above about 9. Forexample, the mixture can be treated at a pH above about 10.

For example, the reactor can have two electrodes. For example, thereactor can have four electrodes. For example, the reactor can have morethan four electrodes.

For example, the electrodes can be cylindrical. For example, theelectrodes can be flat.

For example, the at least one anode and at least one cathode cancomprise a conductive material. For example, the conductive material cancomprise stainless steel or iron. For example, the conductive materialcan be stainless steel. For example, the stainless steel can beperforated stainless steel. For example, the perforated stainless steelcan be stainless steel 316L. For example, the conductive material can becoated with a coating chosen from stainless steel mesh, carbon mesh or atextile. For example, the coating can be stainless steel mesh. Forexample, the stainless steel mesh can have a mesh size of about 200 μm.

For example, the at least one anode and at least one cathode can becylindrical. For example, the at least one anode and at least onecathode can be flat.

For example, the at least one type of pathogen can be a virus, abacteria, a spore, an ova, or mixtures thereof.

For example, the at least one type of pathogen can be Salmonella,Ascaris eggs, C. perfringens, E. coli, or mixtures thereof.

For example, the at least one type of pathogen can be Clostridiumperfringens. For example, the Clostridium perfringens can be in the formof spores.

For example, the processes of the present disclosure can carry outdisinfection, for example, the processes can inactivate and/or destroythe vegetative pathogens, for example, a reduction of FC by 3 log out ofa total of 10⁶ or a reduction of fecal streptococci by 90% can beachieved.

For example, the processes of the present application can achieve lessthan 1 PFU Enterovirus per 4 g of dry solids, and less than 100 MPNfecal streptococci in 1 g of dry solids. For example, in the processesof the present disclosure, less than 3 helminthes ova per 10 g of drysolids and a log 4 reduction of C. perfringens spore can also beachieved.

For example, in the processes of the present disclosure, a log 5reduction of Clostridium perfringens spores can be achieved, and lessthan 1 viable helminth ova in 1 kg of dry solids can be observed, aswell as both Salmonella and fecal coliform can be substantially absentin 25 g of dry solids.

For example, in the processes of the present disclosure, a log 8reduction of Clostridium perfringens spores can be reached.

For example, the processes of the present disclosure can be effectivefor destroying the cell structure of spores.

For example, the processes of the present disclosure can be effectivefor destroying viruses (e.g. up to a log 11 reduction).

For example, the processes of the present disclosure can be effectivefor destroying E. coli (e.g. up to a 10⁶ reduction).

For example, the processes of the present disclosure can be effectivefor destroying Salmonella (e.g. up to a 10⁴ reduction).

For example, the reactor can have one or more outlets for removal of theseparated water.

For example, the reactor can have a vessel installed underneath each ofthe at least one anode and at least one cathode for collectingelectroosmotic flow. For example, the vessel can comprise a bottle, apipe or a reservoir.

For example, the peracid or source thereof can be a source of peracid.For example, the source of peracid can be a composition comprising aperoxygen source and an acylating agent. For example, the peroxygensource can be chosen from a percarbonate, a perborate and a persulfate.For example, the peroxygen source can be a percarbonate. For example,the percarbonate can be sodium carbonate peroxyhydrate. For example, theacylating agent can be an acetylating agent. For example, theacetylating agent can be tetraacetyl ethylene diamine.

For example, the composition comprising a peroxygen source and anacylating agent can further comprise an acid. For example, the acid canbe chosen from an organic acid, sulfamic acid, phosphoric acid, sulfuricacid and hydrochloric acid. For example, the organic acid can be chosenfrom acetic acid, citric acid and formic acid. For example, the organicacid can be citric acid.

For example, the composition comprising a peroxygen source and anacylating agent can further comprise a sequestering agent. For example,the sequestering agent can be chosen from ethylenediaminetetraaceticacid, nitriloacetic acid or a phosphonic acid based sequestering agent.

For example, the composition comprising a peroxygen source and anacylating agent can further comprise a surfactant. For example, thecomposition comprising a peroxygen source and an acylating agent canfurther comprise a corrosion inhibitor.

For example, the composition comprising a peroxygen source and anacylating agent can be a solid composition. For example, the compositioncomprising a peroxygen source and an acylating agent can be in a powderform.

For example, the peracid or source thereof can be a peracid. Forexample, the peracid can be peracetic acid.

For example, the ammonium salt can be chosen from ammonium acetate,ammonium bromide, ammonium carbamate, ammonium carbonate, ammoniumchloride, ammonium fluoride, ammonium formate, ammonium hydrogenoxalate,ammonium hydrogensulfate, ammonium iodide, ammonium nitrate, ammoniumoxalate, ammonium sulfate and mixtures thereof. For example, theammonium salt can be ammonium nitrate.

For example, the processes of the present disclosure can be effectivefor disinfecting the residual. For example, the processes of the presentdisclosure can be effective for pasteurizing the residual. For example,the processes of the present disclosure can be effective for sterilizingthe residual.

For example, the processes of the present disclosure can be effectivefor inactivating at least 4 log of the at least one type of pathogen.For example, the processes of the present disclosure can be effectivefor inactivating at least 5 log of the at least one type of pathogen.For example, the processes of the present disclosure can be effectivefor inactivating at least 6 log of the at least one type of pathogen.For example, the processes of the present disclosure can be effectivefor inactivating at least 7 log of the at least one type of pathogen.For example, the processes of the present application can be effectivefor inactivating the at least one type of pathogen by at least 8 log.

For example, the processes of the present disclosure can be effectivefor carrying out a destruction of at least 4 log of the at least onetype of pathogen. For example, the processes of the present disclosurecan be effective for carrying out a destruction of at least 5 log of theat least one type of pathogen. For example, the processes of the presentdisclosure can be effective for carrying out a destruction of at least 6log of the at least one type of pathogen. For example, the processes ofthe present disclosure can be effective for carrying out a destructionof at least 7 log of the at least one type of pathogen. For example, theprocesses of the present application can be effective for carrying out adestruction of the at least one type of pathogen by at least 8 log.

For example, the treated residual can be suitable for use in anagricultural purpose.

For example, the residual can be a treated or untreated sewage sludge, atreated or untreated industrial sludge or a treated or untreatedagricultural sludge. For example, the residual can be a sewage sludge.

The processes of the present disclosure are, for example apasteurization or disinfection or sterilization technology which hasshown promising results for upgrading residuals to high qualitystandards. By controlling, for example, the electrochemical processes,which can generate temperature with time (up to about 70° C., from about70° C. to about 95° C. and above about 95° C.) leading to a logreduction of pathogens of about 3, about 5 and about 9 respectively. Itis expected to provide, for example, an inexpensive and reliable meansof producing a readily usable and valuable high standard P1 (Class A)product and by EU regulations, an acceptable residual material. The mosteminent characteristics of the processes of the present disclosure canbe described as follows:

First, the application of a low voltage gradient electric field (forexample, less than about 8 V/cm) enhanced with a peracid or a sourcethereof, for example, Bioxy S (BS) and an ammonium salt (AN) providesthe benefit of low energy consumption. Furthermore, the appliedenhancement agents (EAs), for example, BS and AN do not createdisinfection byproducts (DBPs) which would be harmful to human health insuch a way that human exposure to them needs to be restricted. BS is abiocide and strong oxidant which is rapidly converted to carbonic acidand sodium carbonate. It is used for disinfection of equipment in thefood industry. Ammonium components can be found in fertilizers and havevery little effect on pH level in the soil. In the residual matrix, theammonium salt, increases the electrical conductivity of the residual,increasing the efficiency of the treatment system. The ammonium salt canalso liberate ammonia, which acts as a biocide.

Second, it has been shown that the processes of the present disclosurehave the ability, for example to eradicate one of the most resistantforms of microorganism, Clostridium perfringens spores, in anaerobicallydigested residuals (for example, biosolids) within two hours. Hence, theprocesses of the present disclosure can be effective on resistantmicroorganisms, and are a fast treatment technology to achieve saferesiduals which can be widely used and handled without restriction.Conventional methods such as composting, thermal drying, digestiontechnologies and lime stabilization either are not effective on sporesor need a minimum treatment time of at least 72 hours.

Further, the processes of the present disclosure can, for example raisethe temperature of the material to above about 97° C., effectivelykilling most pathogens and creating an environment that will not supportfuture pathogen regrowth.

Simultaneous dewatering of the residual is another advantage of theprocesses of the present disclosure. The treated residual may not, forexample require a further dewatering process. The separated water can,for example be reused directly in irrigation.

Compared to other methods of producing Class A biosolids and residualsacceptable by EU regulations, the processes of the present disclosureare expected to be inexpensive in both initial capital expenditure andongoing operation and maintenance costs. The equipment can be fullyautomated and requires very little operator time.

The following non-limiting example is illustrative of the presentapplication:

Example 1

The BioElectro™ processes of the present disclosure are an innovativeapplication of low voltage gradient in, for example, direct electricfield technology to treat a residual. It is a technology that combinesat least two functions in one: dewatering and pathogen destruction asper BNQ-P1 regulatory compliance (USEPA requirements for class A) aswell as regulations in all European Union countries and qualityimprovement which permits more unrestricted, beneficial uses ofresiduals. It requires a low energy source in the form of, for example,direct current (DC), and offers a suitable technology for a low-techsolution to sludge management applicable to all regions around theworld.

The processes of the present disclosure can be based on the applicationof a low voltage gradient in, for example, a direct electric field withtwo enhancing agents (EAs): Bioxy S (BS) and an ammonium salt, forexample, ammonium nitrate (AN). The concentration of BS and AN usedincreases the conductivity of the sewage sludge. Further, thedisinfection role of BS and AN, at the applied concentrations, withoutapplication of the electrical field would be negligible. The process wasconducted in laboratory size prototype BioElectro™ equipment consistingof a regulated power supply and a 3,100 mL rectangular BioElectro™reactor (FIG. 1) with internal dimensions of 214 mm length×214 mmwidth×74.1 mm height. The reactor 10 comprises four electrodes 12 and arectangular housing 14 that is effective for receiving the residual 16.The electrodes 12 can comprise 2 cathodes and 2 anodes. The electrodescan be flat, circular, perforated or not and they can have variousconfigurations. The electrodes can also be concentric. The power supplytransforms alternating current (AC) from a utility line (120-V, 60 Hz)into high voltage AC, then rectifies to DC signals. The BioElectro™reactor can be equipped with four perforated stainless steel (316L)electrodes (cylinders 10 mm in diameter, 102 mm long) coated with mesh(200 μm), for example, stainless steel mesh, located at a distance of172 mm from each other in proximity of outlet (see FIGS. 2A and 2B).Underneath each electrode, a 200 mL bottle was installed to collectelectroosmotic flow (EOF) during the experiment.

A considerable effort has been made to identify indicator microorganismswhose presence would suggest that human pathogens might be present inthe residual. C. perfringens is a spore-forming thermophilic bacteriumand its spore has been suggested as an indicator for inactivationmechanisms other than temperature as it is resistant to temperature.This organism is found in densities of about 10⁶ colony forming units(CFUs) per gram of solids in raw biosolids (Reimers (2002)).

The process starts by adding BS and AN to the sewage sludge (the ratioof BS to AN can be about 0.5 to about 2 g/g or can be about 0.1 to about2 g/g). The prepared suspension is then dispersed into BioElectro™reactors with a working volume of 2,800 mL. Electrokinetic (EK)phenomena are generated by applying an electrical current between theelectrodes such that at least one of the electrodes functions as ananode and at least one of the electrodes functions as a cathode. A flowof water is induced from the sludge towards the outlets due to theapplied electric field. Accordingly, the sludge is dewatered. Thedewatering process eliminates water, raises the concentration of solidsand reduces sludge volume, thus reducing the costs of further treatmentand handling. Simultaneously, the destruction of Clostridium perfringensspores is achieved after two hours treatment of the sewage sludge. Theeffective near sterilization conditions (>8 log reduction of spores) areobtained at constant voltage gradients of less than about 5 V/cm in thepresence of BS and AN.

The studies of the present disclosure showed that voltage gradient, BSand AN are not sufficiently effective when used alone. In other words,spore inactivation and/or destruction could be obtained only through theinteractive disinfection of voltage gradient and the enhancement agentsBS and AN.

Without wishing to be bound to such a theory, the mechanism ofdisinfection suggests that different factors which attack numerous sporeconstituents, including spore coats, proteins, unsaturated lipids,respiratory enzymes and peptidoglycans are involved in the inactivationand/or destruction of C. perfringens spores in the processes of thepresent disclosure. For example, reactions taking place due to the EKphenomena help to create effective oxidative zones, which neutralizeprotective systems inside and outside of C. perfringens spores. Thegenerated oxygen-based free radicals diffuse to targets within the sporeprotoplast, possibly in the core membrane, and impair the spores.Without wishing to be bound to such a theory, the mechanism of sporeinactivation and/or destruction under the influence of an electric fieldmay include: (1) significant alteration in spore shape and surfaceproperties such as hydrophobicity and net surface charge; and (2) changein the configuration of membrane components such as lipids. All of theseimpacts can potentially lead to irreversible permeabilization of themembrane, resulting in leakage of crucial cytoplasmic components. Thebreakdown of spore membranes and creation of nicks under the studiedconditions was observed in treated spores (FIG. 3).

Along with the action of the electric field on the spores,electrochemical redox reactions (FIG. 4) which occur simultaneously onthe electrode surfaces, facilitate the production of toxic hydrogenperoxide and chlorine or subsequent hypochlorous acid, both of which mayinfiltrate into the inner part of the spores and hasten the inactivationand/or destruction process. Induced electrochemical reactions also bringabout large pH changes in the localized vicinity of the electrodes.Therefore, the pH of the sewage sludge increased significantly, to alevel that ruptures disulfide bonds in the spore coats and leads tohydrolysis of cortex. Moreover, at the elevated pH (>10.7), AN has ahigher spore inactivation and/or destruction power. This is attributedto the generation of ammonia in the molecular form (NH₃) rather than theionized form (NH₄ ⁺).

Without wishing to be bound to such a theory, the direct current alsohelps germination of spores and lowers their resistance to harshconditions due to: (1) sub-lethal heat (above about 62° C. for exampleat about 62 to about 95° C.) generated during the treatment which begetsalterations in the permeability of the spore coats and opening of achemical bond between dipicolinic acid (DPA) and spore enzymes; and (2)an electrokinetically deployed reduction state at the cathodic side ofthe BioElectro™ reactor ruptures disulfide bonds in the spore coats andbrings about hydrolysis of cortex. Moreover, ohmic heating producedduring the process brings about degradation of the spore cortex, andmakes the membrane dysfunctionally permeabilized, causing cell death.FIG. 5 shows the lethal pathways in the processes of the presentdisclosure. FIG. 6 is an exemplary plot showing the log reduction ofClostridium perfringens spores over time in an anaerobically digestedresidual treated with a process of the present disclosure.

The person skilled in the art would understand that the variousproperties or features presented in a given embodiment can be addedand/or used, when applicable, to any other embodiment covered by thegeneral scope of the present disclosure.

The present disclosure has been described with regard to specificexamples. The description was intended to help the understanding of thedisclosure, rather than to limit its scope. It will be apparent to oneskilled in the art that various modifications can be made to thedisclosure without departing from the scope of the disclosure asdescribed herein, and such modifications are intended to be covered bythe present document.

All publications, patents and patent applications are hereinincorporated by reference in their entirety to the same extent as ifeach individual publication, patent or patent application wasspecifically and individually indicated to be incorporated by referencein its entirety. Where a term in the present application is found to bedefined differently in a document incorporated herein by reference, thedefinition provided herein is to serve as the definition for the term.

REFERENCES

-   Blanker, E. M., Little, M. D., Reimers, R. S., and Akers, T. G.,    “Evaluating the Use of Clostridium Perfringens Spores as Indicator    of the Presence of Viable Ascaris eggs in Chemically Treated    Municipal Sludges,” Proceedings of Municipal Sludge (Biosolids)    Management—Where We Are and Where We're Going (Volume I), Water    Environmental Specialty Conference Series, Alexandria, Va., pp.    187-201 (July, 1992).-   Elektorowicz, M.; Safaei, E.; Oleszkiewicz, J. and Reimers, R.    Electrokinetic remediation of biosolids through inactivation of    Clostridium perfringens spores. 6^(th) Symposium on Electrokinetic    Remediation (EREM), 2007.-   Oleszkiewicz J. A. (2012) Sludge management in the European Union:    directives and practice, CSCE/PZITS, 10^(th) Int. Conference on    Water Supply and Quality, Stare Jablonki, Poland.-   Reimers, R. S.; Oleszkiewicz, J. A.; Bowman, D. D and    Faulmann, E. L. (2002) PEC application for the national    classification of the J-Vap process to the category of PFRP, Report    for Paradigm International, Inc. Louisiana, USA.-   Safaei Takhtehfouladi, E., Inactivation of Clostridium perfringens    spore in anaerobically digested biosolids during BioElectro™    process, PhD thesis, Concordia University, Montreal, QC, Canada,    2007.-   Safaei Takhtehfouladi, E. Enhanced electrokinetic (EK) technology: A    comparative study for inactivation of Clostridium perfringens spores    and reovirus in anaerobically digested biosolids. Master's thesis,    Concordia University, Montréal, QC, Canada, 2007.-   Safaei, E. and Elektorowicz M. Bench-scale trial of electrokinetic    treatment on anaerobically digested biosolids: Microbial    inactivation, 8^(th) World Congress of Chemical Engineering; Canada,    2009.

What is claimed is:
 1. A process for treating a residual, said processcomprising: preparing a mixture by adding: a peracid or source thereof;and an ammonium salt to the residual, the ratio of the peracid or sourcethereof to the ammonium salt being 0.1 g/g to 5 g/g and the peracid orsource thereof and ammonium salt being added to the residual at lessthan 40 g peracid or source thereof and ammonium salt per liter of theresidual, said mixture having a pH above 9; and treating the mixture ina reactor with an electric field, wherein the electric field is a directcurrent electric field and the voltage gradient of the direct currentelectric field is less than 8 V/cm, by means of at least one anode andat least one cathode that define therebetween an electrokinetic zone fortreating the mixture so as to cause an exothermic reaction, wherein themixture is treated at a temperature of 70° C. to 99° C. for a time of0.5 hours to 4 hours; thereby allowing for inactivation of least onetype of pathogen selected from a virus, a bacteria, a spore, an ova or amixture thereof in the residual, so as to obtain a treated residual. 2.The process of claim 1, further comprising simultaneous dewatering ofthe residual so as to obtain a treated dewatered residual and separatedwater.
 3. The process of claim 1, wherein the at least one anode and atleast one cathode comprise a conductive material and the conductivematerial is coated with a coating chosen from stainless steel mesh,carbon or a textile.
 4. The process of claim 2, wherein the at least oneanode and at least one cathode comprise a conductive material and theconductive material is coated with a coating chosen from stainless steelmesh, carbon or a textile.
 5. The process of claim 1, wherein the atleast one anode and at least one cathode are cylindrical and perforated.6. The process of claim 1, wherein the at least one type of pathogenincludes Clostridium perfringens and the Clostridium perfringens is inthe form of spores.
 7. The process of claim 5, wherein the at least onetype of pathogen includes Clostridium perfringens and the Clostridiumperfringens is in the form of spores.
 8. The process of claim 1, whereinthe reactor has a vessel associated with at least one of the at leastone anode and at least one cathode for collecting electroosmotic flow.9. The process of claim 5, wherein the reactor has a vessel associatedwith at least one of the at least one anode and at least one cathode forcollecting electroosmotic flow.
 10. The process of claim 1, wherein theperacid or source thereof is a peracetic acid.
 11. The process of claim2, wherein the peracid or source thereof is a peracetic acid.
 12. Theprocess of claim 9, wherein the peracid or source thereof is a peraceticacid.
 13. The process of claim 10, wherein the mixture further comprisesa surfactant.
 14. The process of claim 11, wherein the mixture furthercomprises a surfactant.
 15. The process of claim 12, wherein the mixturefurther comprises a surfactant.
 16. The process of claim 13, wherein theammonium salt is ammonium nitrate.
 17. The process of claim 14, whereinthe ammonium salt is ammonium nitrate.
 18. The process of claim 15,wherein the ammonium salt is ammonium nitrate.
 19. The process of claim18, wherein the process is effective for inactivating or carrying out adestruction of at least 7 log of the at least one type of pathogen. 20.The process of claim 1, including treating the mixture so as to allowfor spore germination and/or permeabilization of spore membranes.